LITTLE ROCK (AP) — More than 55,000 low-income Arkansans have told the state they want to sign up for coverage under a recently approved plan to use Medicaid funds to purchase private insurance under the federal health care law, the Department of Human Services said Wednesday.

The department said it planned to begin mailing out letters to the 55,440 people instructing them on how to enroll in the state’s “private option,” approved by the federal government last week as an alternative to expanding Medicaid’s enrollment under the federal health care law.

“This clearly shows there was a need for the unique approach that Arkansas took to help ensure the lowest-income Arkansans have access to quality health insurance,” DHS Director John Selig said in a written statement.

Under the private option law, Arkansas will use federal money to buy private insurance for about 250,000 eligible low-income residents. The program allows people who earn up to 138 percent of the poverty line — or $15,415 per year — to buy subsidized private insurance through the state’s insurance exchange.

The Republican-led Legislature and Democratic Gov. Mike Beebe approved the private option in April as an alternative to expanding Medicaid. Several other states have expressed interest in a similar program.

Open enrollment in the exchange began Tuesday and runs through March 31.

DHS spokeswoman Amy Webb said the department mailed letters to 154,420 people it had identified through the Supplemental Nutrition Assistance Program as eligible for the private option. Through the letters, the state was also able to enroll 2,539 previously uninsured children in its ARKids First health coverage program.

The potential participants had to sign a form signaling their interest and acknowledging that the private option coverage could end at any moment. That acknowledgement was required under the state law setting up the expanded insurance program.

DHS announced the numbers the day after the state launched the insurance exchange, an online marketplace where consumers can compare policies and purchase insurance. About half of the 500,000 people expected to participate in the exchange are doing so under the private option.

The state Insurance Department said it didn’t have figures yet on the number of Arkansans who have so far enrolled in the exchange. High demand on the federal website has prevented some Arkansans from applying online. Applying by mail and phone are also options.

A spokeswoman for the Insurance Department said more than 22,000 people visited the state’s exchange website Tuesday, and 13,700 of those visitors went on to the federal site.